Albert Einstein, a physicist, became the public face of science in the 20th century. But it was German-Jewish chemist Fritz Haber, arguably the greatest industrial chemist who ever lived, who did vastly more to shape our world.

Because of Haber, industrially produced nitrate fertilizers produce vastly more fertile crops across North America and Europe than was dreamed possible 100 years ago. America’s vast, regular global wheat exports and the success of the EU’s Common Agricultural Policy would not be possible without the work of Fritz Haber.

However, the 20 million deaths of World War I, the Russian Revolution, the rise of Adolf Hitler and the Holocaust would never have happened without Haber either. When the British sea blockade cut Germany off from its vital raw materials at the beginning of World War I, it was Haber who developed the techniques to produce nitrate explosives from ammonia in gigantic chemical plants that enabled Germany to fight on for another four years.

Haber invented a large-scale catalytic synthesis of ammonia from elemental hydrogen and nitrogen gas, reactants that are abundant and inexpensive in nature. He used exceptionally high temperatures and pressures to convert nitrogen into nitrate fertilizer in previously unimaginable quantities.

Haber deservedly won the Nobel Prize for chemistry for this 1908 achievement, without which the Green Revolution of “miracle” strains of genetically engineered high-yield rice would not have been possible.

Haber therefore revolutionized the entire course of world history. The transformation of Asia and the emergence of China and India as giant, modern 21st-century global economies would never have been possible without Norman Borlaug’s miracle rice strains. But they could never have been grown had Haber not “extracted bread from air,” as his fellow Nobel laureate Max von Laue put it. Borlaug’s “miracle” strains of rice and grain require exceptionally vast inputs of the nitrate fertilizer that is still made from the process Fritz Haber discovered.

These fertilizers also require enormous inputs of oil. This means the dream of an oil-free world can never happen. Even if eternal, ever-renewable free energy could be harnessed from the sun or the cosmic currents of space, a world of seven billion people would still be desperately dependent on oil to make the nitrate fertilizer to grow the crops those people need to survive. The 21st century, like the 20th century, therefore, will still be Fritz Haber’s world.

But Haber also had other “achievements” to his name. Seriously complicating his legacy is the fact that some 650,000 people were killed or horribly maimed in World War I, mainly on the Western Front, through the use of poison gas warfare. And Haber was the driving force, visionary genius and chief experimenter who made it all possible. He even personally supervised the very first poison gas attack in history against British troops at Ypres on April 22, 1915.

He developed an industrially applicable synthesis of ammonia and masterminded the great ammonia factories that produced the nitrates for explosives without which Germany could not have fought on for three more years. Were it not for Haber’s dedication to his country, the Russian Revolution and the hecatombs of slaughter presided over by Lenin, Stalin and Hitler might never have happened.

Haber was for generations regarded, especially in Britain and France, as a repulsive, exaggerated monster. Instead, the figure that emerges from “Master Mind: The Rise and Fall of Fritz Haber,” the currently definitive biography of him by Daniel Charles, is all too familiar.

Haber was brilliant, and knew it, and was hungrily ambitious to get on in the world. He was in no way a racist but was a passionate German patriot who eagerly grasped every financial and honorific award that his vast services to his nation offered him.

Haber was for most of his life oblivious of his Jewishness until the Nazis forcibly reminded him of it. He had converted to Christianity in his youth, though only pro forma. He saw conversion, as the great poet Heinrich Heine had three quarters of a century before, as his “ticket” into mainstream European civilization. And like Heine, he repented virtually on his death bed, though he had a lot more than Heine to repent for.

Haber had many admirable human qualities. He was warm, gregarious, generous and outgoing. He loved good jokes and was a loyal and devoted friend who helped Einstein through Einstein’s divorce from his first wife. He attracted a circle of brilliant and devoted young scientists around him, including future Nobel Prize winner James Franck and the great Lise Meitner, who with Otto Hahn made the crucial breakthrough in nuclear fission.

But a curse, closely associated with Haber’s hideous enthusiasm for developing poison gas, afflicted his personal life. His first wife, the hauntingly beautiful and sweetly idealistic Clara Immerwahr, also of Jewish background, and a fine scientist herself, committed suicide with Haber’s own Army revolver when he was back on leave just after triumphantly supervising the very first poison gas attack. Ever the meticulous scientist, she test-fired a shot in the garden to make sure the mechanism was working, then blew her own brains out.

Their 12-year-old son Hermann was the first to find his dying mother. Some 31 years later, Hermann, distraught over his own beloved wife’s early death from leukemia, committed suicide too. So did his own eldest daughter.

Haber remarried. According to one story, Clara discovered him on the night of her own suicide in the arms of his far younger future second wife, Charlotte. That marriage ended in divorce too. Einstein rescued Charlotte, her two children and Hermann and his family from the Nazis.

Haber, the anti-hero of this awful, riveting story, embodied in his own life the two-faced, Janus-like nature of modern science, providing unimagined advances in prosperity and health on the one hand, and inconceivable tools to inflict suffering and evil on the other.

His life is also a cautionary tale of the evil consequences of a conscience-free, grasping ambition and vanity and a drunken perversion of healthy patriotism.

Even Haber’s most innocent-seeming activities turned out to have global — and catastrophic — consequences.

He produced, almost as an afterthought of his poison gas research, a useful garden insecticide called hydrogen cyanide and then forgot about it.

A quarter of a century later, this same insecticide, with its warning-indicator odor removed and relabeled Zyklon B, killed millions of innocent European Jews in the extermination camps of Auschwitz and Majdanek. The children and grandchildren of Fritz Haber’s sisters were among its myriad victims.